The central actions and possible roles of angiotensin I, II and III in the elevation of arterial blood pressure will be investigated in both anesthetized and awake cats and dogs. In addition, the effects of angiotensin I and II, administered via the cerebral lateral ventricles of anesthetized cats on peripheral renin secretion will be investigated. Previous data have indicated that an increase in the levels of angiotensin II in the cerebrospinal fluid markedly increases both systolic and diastolic pressure, which is due mainly to an increase in peripheral resistance, especially in the mesenteric vascular beds. Studies have been designed to investigate the effects of intraventricular administration of angiotensin I and II on peripheral renin release, renal function and sympathetic flow to the renal arteries. Effects of chronic administraion of angiotensin II via the lateral ventricles of awake cats and dogs will also be investigated.